The rationale for non-performance-first code is that they need to get features out fast to stay relevant. Most devs who would use an open-source framework wouldn't care how fast it is, as long as it's not ridiculous. They care that it can do X, Y, and Z. Tech giants DO care about small speed improvements, though. This could provide a good counterbalance so that devs are still rewarded for delaying features to make sure their code is high-quality.